The overall goal of this research is to gain a better understanding of the biology of pneumocystis carinii and to apply this knowledge to the development of a rapid and non-invasive diagnostic test for pneumocystosis. Pneumocystis carinii is an opportunistic pathogen that has emerged as an important cause of pneumonia in the immunocompromised host and is particularly important in patients with acquired immune deficiency syndrome (AIDS). Studies on P. carinii have been severely hampered due to the inability to successfully propagate the organism in large quantities in vitro. As a result, little is known about the biochemistry of P. carinii, or about its interaction with host tissues, and subsequently the disease process. In addition, information about the existence os strain variability is lacking. A further understanding of this relevant organism can be achieved, however, by analyzing its antigens and DNA using hybidoma and recombinant DNA technology. The specific aims of this proposal are: 1) To identify cross- reactive epitopes of Pneumocystis species, determine the chemical nature and the localization of these epitopes using monoclonal antibodies; 2) To continue the isolation, purification and biochemical characterization of the major antigens of Pneumocystis using chromatographic techniques: 3) To continue the development and screening of genomic libraries for Pneumocystis -specific DNA probes with emphasis on repetitive sequence clones: 4) To use the recombinant Pneumocystis DNA clones perform restriction fragment-length polymorphism studies on DNA od Pneumocystis isolated from different species: 5) To evaluate the usefulness of the P. carinii monoclonal antibodies and recombinant DNA clones as diagnostic tools for detecting human Pneumocystis in clinical specimens. Dot blot and in situ hybridization and the avidin-biotin complex immunoperoxidase techniques will be used. Results from this study should provide a better understanding of the basic biology of this organism including information on existence of different strains. The availability of purified antigens and information about these specific antigens should facilitate strategies to be devised to better understand the interaction of this parasite with its host. Use of monoclonal antibodies and Pneumocystis-specific DNA clones as diagnostic probes for early detection of pneumocystosis would improve therapeutic intervention and prognosis of individuals in a life-threatening situation.